Pramipexole is currently under development for treatment of schizophrenia and tardive dyskinesia (TD). TD is a syndrome of involuntary movements occurring during or after treatment with neuroleptics. This syndrome affects 15-20% of patients treated with neuroleptics. The objectives of this study are to evaluate the effect of oral escalating doses of pramipexole on tardive dyskinesia; to evaluate safety and tolerance of escalating doses; and to evaluate the pharmacokinetics of multiple doses of pramipexole.